Abstract
BackgroundIn Iran, re-refinery industry has been developed many years ago based on the acid-clay treatment. Acidic sludge with high concentration of total petroleum hydrocarbon (TPH) is the final products of some facilities. In this study removal of TPH by aerated in-vessel composting was investigated.MethodsIn order to microorganisms seeding and nutrient providing, urban immature compost was added as an amendment to acidic sludge. The ratios of acidic sludge (AS) to compost were, 1:0 (as control), 1:5, 1:8, 1:10, 1:15, 1:20, 1:30, 1:40, 1:50, 1:75 and 1:100 (as dry basis) at a C: N: P ratio of 100:5:1 and 45–65% moisture content for 70 days.ResultsThe removal efficiency in all reactors was more than 48%. The highest and lowest TPH removal was observed in 1:5 (71.56%) and 1:100 (48.53%) mixing ratios, respectively. The results of the control reactors showed that biological treatment was the main mechanism for TPH removal. Experimental data was fitted second order kinetic model (R2 > 0.8006). Degradation of TPH in 1:5 mixing ratio (k2 = 0.0038 gmg −1d−1; half-life = 3.08d) was nearly three times faster than 1:100 mixing ratio (k2 = 0.0238; half-life = 8.96d). The results of the control reactors showed that biological treatment was the main mechanism for TPH removal.ConclusionThe results of this study revealed in-vessel composting with immature urban compost as the amendment maybe recommended as an effective method for TPH remediation.
Highlights
In Iran, re-refinery industry has been developed many years ago based on the acid-clay treatment
It is obvious that the acidic sludge contains high concentration of Zn, Cu, Fe, Mo, B with exceeding 1000 mg/kg
Characteristics of the acidic sludge and immature compost As it clears more than 50% of acidic sludge mass containing by total petroleum hydrocarbon (TPH), and pH in this type of sludge is extremely acidic
Summary
In Iran, re-refinery industry has been developed many years ago based on the acid-clay treatment. Acidic sludge with high concentration of total petroleum hydrocarbon (TPH) is the final products of some facilities. Million tons of used oil are collected from repair shops and are taken to larger facilities which are called re-refineries and their contaminants are separated [1]. Sludge Produced by Re-refinery Industries contain a material that are considered to be potent carcinogen and immunotoxicant. The acidity of this oily sludge (pH 1.5–3) of is owing to sulphuric acid that was consumed in old wax refining methods in the refinery [12]
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